INVIVO AND INVITRO RELEASE OF IVERMECTIN FROM POLY(ORTHO ESTER) MATRICES .1. CROSS-LINKED MATRIX PREPARED FROM KETENE ACETAL END-CAPPED PREPOLYMER

Release of ivermectin from a crosslinked poly(ortho ester) matrix was studied both in vitro and in vivo in rats and dogs. A total of 32.8% o f the loaded drug was covalently bonded to the polymer matrix. The rel ease rate of the drug in vitro was initially slow but accelerated in t he later stages of the studies. The rat plasma concentration of the dr ug was maintained fairly constant over a period of 6 months with a sli ght increase thereafter. Implant retrieval studies in dogs showed that the drug release may be controlled by matrix erosion.